Questions tagged [code-challenge]

A code challenge is a competition for creative ways to solve a programming puzzle with an objective winning criterion not covered by other scoring tags (e.g. code-golf).

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1007
votes
6answers
213k views

Build a working game of Tetris in Conway's Game of Life

Here is a theoretical question - one that doesn't afford an easy answer in any case, not even the trivial one. In Conway's Game of Life, there exist constructs such as the metapixel which allow the ...
478
votes
1answer
148k views

Build a digital clock in Conway's Game of Life

Your task is to build a Game of Life simulation representing a digital clock, which satisfies the following properties: The clock displays the hours and minutes in decimal (e.g. ...
372
votes
17answers
82k views

Build a Compiler Bomb

Introduction You're probably familiar with zip bombs, XML bombs, etc. Put simply, they are (relatively) small files which produce enormous output when interpreted by naïve software. The challenge ...
311
votes
8answers
27k views

Upgoat or Downgoat?

Given an image of a goat, your program should best try to identify whether the goat is upside down, or not. Examples These are examples of what the input may be. Not actual inputs Input: Output: <...
299
votes
23answers
38k views

Write Moby Dick, approximately

Here is a 1.2Mb ASCII text file containing the text of Herman Melville's Moby-Dick; or, The Whale. Your task is to write a program or function (or class, etc. -- see below) which will be given this ...
280
votes
141answers
476k views

I need a program where the user inputs an array of doubles and the program outputs the array sorted

Note: This question was severely edited since I first posted it here. The rules were moved to here, read them before posting any answer to understand the purpose of this. This was the first question ...
241
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36answers
43k views

Paint Starry Night, objectively, in 1kB of code

Note: Anders Kaseorg has been awarded the accept for now, to draw attention to his great answer, but the challenge is by no means over! There is still a 400 point bounty in the offering for anyone who ...
228
votes
115answers
32k views

Without using numbers, get the highest salary you can. But don't exaggerate!

As I'm applying for some jobs whose job advert doesn't state the salary, I imagined a particularly evil interviewer that would give the candidate the possibility to decide their own salary ...by "...
183
votes
144answers
17k views

What is the smallest positive base 10 integer that can be printed by a program shorter (in characters) than itself?

I think the question as above is clear, but just in case: Write a full program (not just a function) which prints a positive base 10 integer, optionally followed by a single newline. Qualifying ...
157
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63answers
22k views

How high can you count?

Challenge: Your task is to write as many programs / functions / snippets as you can, where each one outputs / prints / returns an integer. The first program must output the integer ...
115
votes
73answers
24k views

Largest Number Printable

Your goal is to write a program that prints a number. The bigger the number, the more points you'll get. But be careful! Code length is both limited and heavily weighted in the scoring function. Your ...
114
votes
16answers
15k views

Implement the Game of Life on Anything but a Regular Grid

Conway's Game of Life is (almost) always played on a regular square grid, but it doesn't need to be. Write a program that implements the standard cell neighboring rules from Conway's Game of Life on ...
113
votes
24answers
16k views

Lab Rat Race: an exercise in genetic algorithms

This is Fortnightly Challenge #3. Theme: Genetic Algorithms This challenge is a bit of an experiment. We wanted to see what we could do, challenge-wise, with genetic algorithms. Not everything may be ...
108
votes
51answers
15k views

Fewest (distinct) characters for Turing Completeness

Summary: For any given language, what is the smallest amount of unique characters for your language to be Turing-Complete? Challenge: For any language of your choice, find the smallest subset of ...
102
votes
37answers
6k views

Source code ecological footprint

You've just been hired by a German car manufacturing company. Your first task, as an engineer, is to write a program that computes the ecological footprint of ASCII strings. The ecological footprint ...
101
votes
32answers
11k views

What are the five most powerful characters in your language?

Choose any five characters your language supports. There are 5! = 5×4×3×2×1 = 120 ways these can be arranged into a 5-character string that contains each character once; 120 ...
100
votes
15answers
89k views

Generate the longest error message in C++

Write a short program, that would generate the longest possible error message, in a standard C++ compiler (gcc, cl.exe, ...
95
votes
346answers
16k views

One OEIS after another

As of 13/03/2018 16:45 UTC, the winner is answer #345, by Scrooble. This means the contest is officially over, but feel free to continue posting answers, just so long as they follow the rules. As ...
93
votes
36answers
11k views

The Versatile Integer Printer

Write a piece of code that is executable in at least three different languages. The code must output the integer 1 in language number one, ...
93
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83answers
9k views

Unique is Cheap

Write a function or program that determines the cost of a given string, where the cost of each character equals the number of how many times the character has occurred up to this point in the string,...
92
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18answers
16k views

When was this language released?

Your challenge is simple. You need to write a program that prints to either STDOUT or a file the year the language it is written in was released. Because this is such a simple task, the twist is that ...
92
votes
11answers
12k views

Build a Markdown bomb [closed]

I'm sure most of us have heard of zip bombs and similar decompression bomb tricks, where a maliciously crafted input creates a massively disproportionate output. We even had a question on here to do ...
87
votes
33answers
16k views

Eww, those bytes are gross

Write a program or function that, when given a string, filters out as many distinct bytes as it can and returns the cleaned string. However, since your program hates them, none of these bytes can be ...
85
votes
46answers
7k views

Find an Illegal String

The challenge is to find a string of characters that cannot appear in any legal program in your programming language of choice. That includes comments, strings, or other "non-executable" parts. ...
84
votes
54answers
11k views

Can you outgolf me? (Cops section)

Cops section The robbers section can be found here. Thanks to FryAmTheEggman, Peter Taylor, Nathan Merrill, xnor, Dennis, Laikoni and Mego for their contributions. Challenge Your task is to write ...
81
votes
9answers
16k views

Counting Grains of Rice

Consider these 10 images of various amounts of uncooked grains of white rice. THESE ARE ONLY THUMBNAILS. Click an image to view it at full size. A: B: C: D: E: F: G: H: I: J: Grain Counts:...
78
votes
55answers
13k views

-ENDED- Do something that looks like something else [closed]

Write a snippet, a function, a programm, ... that is obfuscated in a way that it looks clear at the first sight that it does something else. For example: write a bit of code that adds two number, but ...
77
votes
69answers
15k views

Largest number in ten bytes of code

Your goal is to print (to the standard output) the largest number possible, using just ten characters of code. You may use any features of your language, except built-in exponentiation functions. ...
73
votes
15answers
10k views

Hello World in Multiple Languages

Task Create a program or a function that is valid in multiple programming languages, and when compiled/interpreted as a different language outputs "Hello, World!" in a different natural language. ...
73
votes
24answers
4k views

Tweetable hash function challenge

In this code-challenge you will write a hash function in 140 bytes1 or less of source code. The hash function must take an ASCII string as input, and return a 24-bit unsigned integer ([0, 224-1]) as ...
71
votes
27answers
6k views

2016 Time Capsule String: How Versatile Is Your Language?

About a year ago on Dec 31, 2015, I had the idea that: We should make a time capsule string. Everybody gets to add one character and next new years we'll see who can make the best program out of ...
70
votes
133answers
15k views

The alphabet in programming languages

Our task is to, for each letter of the (English) alphabet, write a program that prints the alphabet, in a language whose name starts with that letter. Input: none Output: ...
69
votes
18answers
10k views

Rube Goldberg Hello World

For this golf, you will need to use more than one language. The task A Rube Goldberg machine is a contraption that takes an enormous number of complicated steps in order to execute a very simple ...
67
votes
7answers
6k views

Fault-Tolerant Hello World (a.k.a. the Interview)

At the end of your interview, the Evil Interviewer tells you, "We make all of our applicants take a short coding test, to see if they really know what they are talking about. Don't worry; it's easy. ...
66
votes
14answers
5k views

Write a polyglot that prints the language's name

Your task is to write a program that executes in as many languages as possible, with as few characters as you can. To avoid trivial solutions, the program must print the name of the language it was ...
65
votes
15answers
17k views

9 Hole Challenge [closed]

The 9 Hole Challenge 9 code golfing challenges of varying difficulty. Penalties for using the same language more than once. The question will be updated with pars, hole champions and trophy winners....
59
votes
10answers
7k views

Encode Images into Tweets (Extreme Image Compression Edition) [closed]

Based on the very successful Twitter image encoding challenge at Stack Overflow. If an image is worth 1000 words, how much of an image can you fit in 114.97 bytes? I challenge you to come up with a ...
56
votes
146answers
6k views

Evolution of OEIS

In this challenge, the goal is to recreate the On-Line Encyclopedia of Integer Sequences one sequence at a time. Similar to the Evolution of Hello World, each answer depends on a previous answer. ...
55
votes
20answers
8k views

Exit Code Golfing

Inspired by this default for IO. The Task Write a program that, given an input integer x between 0 and 255, crashes with exit code ...
54
votes
21answers
5k views

Add a feature to a programming language [closed]

Your task is to tack on a feature to a programming language, either by implementing a very clever library, or by processing the input text and/or tweaking the compilation process. Ideas: Add PHP-...
54
votes
6answers
4k views

ASCII Art Calendar

Let's make an ASCII art clock and calendar that tells us the current month, day of the month, day of the week, hour, minute, and whether it's night or day (but not the year or second). At any ...
54
votes
1answer
3k views

Build a fewest-moves freecell solver

In the game of Freecell, you are tasked with building four foundation piles in suit from ace to king, on a layout where you build downward in alternating colours. However, you can only build one card ...
51
votes
49answers
9k views

Determine your language's version

Your challenge is to write a polyglot that works in different versions of your language. When run, it will always output the language version. Rules Your program should work in at least two versions ...
51
votes
8answers
6k views

1 character typo generating most error messages from C++ compilation

It seems that simple changes to a C++ file, especially with templates, can generate pages of errors. This contest is to see what the largest "bang of the buck" is, that is the more verbose error ...
50
votes
10answers
9k views

Build a random number generator that passes the Diehard tests

While there are many code golf questions on here involving randomness, I haven't seen one yet that actually asks for building an algorithmic pseudorandom number generator. There's this one that asks ...
49
votes
95answers
14k views

Goodbye Cruel World!

Background Hello golfers! I would like to learn all the programming languages! But I kinda have a short attention span... and copying all the Hello World examples gets boring... but I like fire! ^w^ ...
48
votes
25answers
6k views

First code golf decathlon [closed]

Tasks All competitors try to solve the following list of 10 tasks: math Read a positive integer n from input and return the sum of the cubes of the first n non-negative integers. For input ...
48
votes
22answers
5k views

“As we travel the universe…”

You'll be given the name of one of the 20 biggest objects in the Solar System. Your task is to return an approximation of its radius, expressed in kilometers. This is a code-challenge where your ...
48
votes
16answers
7k views

mastermind horse battery staple

Objective Given a list of three-word passphrases, crack them all. Each time you guess, you will be given a clue in the style of Mastermind, depicting how many characters match the password, and how ...
48
votes
3answers
3k views

Shortest universal maze exit string

A maze on an N by N grid of square cells is defined by specifying whether each edge is a wall or not a wall. All outer edges are walls. One cell is defined as the start, and one cell is defined as the ...